In an image coding method of the present invention, after a process such as DCT is performed to digital image data, quantization process is performed, and then, to resultant quantized transform coefficients, variable length coding process is performed with reference to a variable length code table showing how variable length codes are allocated, and in a comparison process between an event derived from the quantized transform coefficients and reference event included in the variable length code table, transformation process is performed to increase a possibility of performing variable length coding with satisfactory coding efficiency.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An image decoding method for extracting a variable length code from compression coded data, comprising obtaining an event corresponding to said variable length code by using a variable length code table wherein a reference event consisting of Last, Run, and Level, is assigned to each reference variable code, and deriving an output transform coefficient from said event, the method further comprising: obtaining an event corresponding to said variable length code by using said variable length code table when said variable length code does not include a control code, obtaining an event corresponding to said variable length code by using said variable length code table and then obtaining a transformed event by tranforming the Level value of said event corresponding to said variable length code using a predetermined function when said variable length code includes said control code followed by a second mode code, and wherein the control code is 0000011 and the second mode is 0 .
2. An image decoding method for extracting a variable length code from compression coded data, comprising obtaining an event corresponding to said variable length code by using a variable length code table wherein a reference event consisting of Last, Run, and Level, is assigned to each reference variable code, and deriving an output transform coefficient from said event, the method further comprising: obtaining an event corresponding to said variable length code by using said variable length code table when said variable length code does not include a control code, obtaining an event corresponding to said variable length code by using said variable length code table and then obtaining a transformed event by transforming the Level value of said event corresponding to said variable length code using a predetermined function when said variable length code includes said control code followed by a second mode code, and wherein the predetermined function for transforming the Level value is defined as: the transformed Level sign ( the resultant Level value) .
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
August 11, 1998
February 5, 2002
Browse 5M+ US patents with plain-English claim translations and AI-generated analysis.